National Weather Service Raw Text Product

492 
FXUS63 KLSX 011739
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1239 PM CDT Tue Oct 1 2013

.UPDATE:
Issued at 921 AM CDT Tue Oct 1 2013

Clouds continue to hold a bit longer than prev anticipated. Based
on early guidance, have kept clouds lingering into the early
afternoon and cooled temps thru the morning. Only minor changes
were made to the max temps expected today as temps shud jump
quickly once clouds begin to break up. 

&&

.SHORT TERM:  (Through Late This Afternoon)
Issued at 215 AM CDT Tue Oct 1 2013

Early this morning:  the upper level ridge has rebuilt into our area 
from the southern plains and lower MS valley, promising to maintain 
the above average temps that have been commonplace since late 
August.  At the surface, a light southerly flow prevails, around the 
backside of an area of high pressure centered over the southern 
Appalachians.  Temps have fallen into the 60s, which is mild for 
this time of year, and any further falls are being hampered by large 
swaths of stratus clouds that have taken off just before midnight 
and are expanding northward with the prevailing wind.  Given the 
mixier environment, visibilities have not suffered much in the way 
of hits unlike last night, with MVFR conditions or better observed.

Visibilities are expected to continue to behave themselves and stay 
above 1 mile for the vast majority of sites but will continue to 
monitor.  The stratus, in the meantime, is expected to expand over 
much of the forecast area, with NE MO being the last to be affected 
or remaining on the edge by 15z, when the stratus should then start 
to dissipate around its edges.  Some areas, however, may not see 
much sun until early afternoon if yesterday was any gage, and have 
went conservative with temp rises today in most places except the 
far north which should get the sun first and longest:  look for max 
temps from the upper 70s in SE MO to the mid 80s in NE MO-W Central 
IL. 

A more moist atmospheric column is expected to build in to our area 
today from the south, with PWs rising to around 1.3" by conservative 
estimates.  The one thing lacking is a decent trigger aloft or at 
the surface, but for lack of anything else, the eastern Ozarks of SE 
MO tend to provide enough local effects to support isolated SHRA in 
an environment anticipated to have little-no CINH. 

TES

.LONG TERM:  (Tonight through Monday)
Issued at 320 AM CDT Tue Oct 1 2013

Will likely have stratus clouds and patchy fog across sern MO and
swrn IL tgt. A weak front will sag swd into nern MO and w cntrl IL
by 12z Wednesday, then lift back n-newd on Wednesday. The chance
of showers and thunderstorms will return to much of the area on
Wednesday as a weak upper level low moves nwd then newd from the
Gulf Coast states and into the Tennessee Valley region, while weak
sw flow shortwaves move newd through the area. Low level moisture
will be also increasing and gradually getting deeper over our area
with increasing instability. Will inclulde chance pops over the
srn two thirds of our forecast area on Wednesday, then over the
entire area on Wednesday ngt. The GFS model appears too high on
pops and qpf for Wednesday ngt. The best potential for convection
on Thursday should be across IL. Despite the low level cloud cover
and scattered convection unseasonably warm weather can be expected
on Wednesday and Thursday with highs at least 10 degrees above
normal. The NAM model develops convection across nrn MO and w
cntrl IL Thursday ngt with a swly low level jet through nwrn MO
over a front sagging sewd into nwrn MO by 12z Friday. Will include
chance pops over this area Thursday ngt, although it appears that
the NAM model may be a little too far south with this front.
Friday should be the last unseasonably warm day with strong s-swly
sfc/low level flow ahead of a developing upper level low over the
nrn Plains and associated surface low moving newd through the
Plains. The best potential for convection, possibly strong will be
Friday night as the deepening surface low moves newd into the nrn
Plains and drags a strong cold front sewd through our area.
Precipitation may continue across the sern half of our forecast
area on Saturday, and then shift se of our forecast area by
Saturday night as much colder and less humid air filters sewd into
the region with 850 mb temperatures dropping to about 4-8 degrees
C. Below normal temperatures can be expected Saturday ngt through
Sunday ngt as a deep upper level trough moves slowly ewd through
the region, possibly closing off into an upper level low.

GKS

&&

.AVIATION:  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1226 PM CDT Tue Oct 1 2013

Expect similar events to unfold tonight as what happened this
morning. Current cloud deck will continue to lift and/or dissipate
this afternoon and evening. ST/FG shud redevelop late tonight and
move back into the region. ST/FG will once again be slow to burn
off and lift tomorrow. Otherwise, sly winds thru the period. 

Specifics for KSTL: Expect similar events tonight as this morning.
Cigs may need to be lowered for late tonight into Wed morning, but
believe trends are in the right direction. Latest guidance
suggests shra with isod ts may impact the terminal late in the TAF
period. With uncertainty in timing, will leave TAF dry for now and
allow future updates to pin down timing. 

Tilly

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX